Poly-Planar MA840 Sub-Compact 3" Dual Cone Box Speakers are designed to fit in difficult locations and still offer quality sound. In addition to being low-magnetic field speakers, the MA840 have the full complement of Poly-Planar marine waterproof and corrosion-proof features that include stainless steel grill and bracket, 4 ohm impedance, plastic enclosure, 40 watts maximum power per speaker, and a dual-cone design with 3" main cone. 4"W x 4.25"H x 4.5"D. Two-year warranty.